bug#23339: 24.5; align-region assumes that match does not contain newline

[Josh <josh+gnu@nispio.net>]

The align-region function assumes that a matching regexp does not
contain a newline.  This causes unexpected behavior in cases where the
first "column" being aligned contains only whitespace.  The following
script exhibits the unexpected behavior:

emacs -Q --eval '(progn
 (switch-to-buffer "*test*")
 (text-mode)
 (setq indent-tabs-mode nil)
 (insert "lorem ipsum, dolor sit amet,\n ,,\n")
 (let ((table (make-syntax-table (syntax-table))))
   ;; (modify-syntax-entry ?\n ">" table) ; <= UNCOMMENT THIS LINE TO FIX
   (with-syntax-table table
   (align-regexp (point-min) (point-max) "\\(\\s-*\\)," 1 1 t))))'

Uncommenting the seventh line and running again will show the expected
behavior.  The fix works around the problem by using a syntax map in
which the newline character does not belong to the whitespace syntax
class, thus preventing \s-* from matching the newline.


In GNU Emacs 24.5.1 (x86_64-apple-darwin13.4.0, NS apple-appkit-1265.21)
 of 2015-04-10 on builder10-9.porkrind.org
Windowing system distributor `Apple', version 10.3.1348
Configured using:
 `configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp''

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Text

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  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

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Memory information:
((conses 16 72780 5795)
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